U.S. permanent representative at the UN Nikki Haley has called for the immediate release of two Iranian Americans, Siamak and Baquer Namazi, currently being held in Tehran.

Siamak, 46, and his octogenarian father, Baquer, have been behind bars at Tehran’s notorious Evin Prison since 2015.

“Detaining political prisoners is one of the worst human rights abuses a country can do. Iran is doing just that with two of our citizens,” Haley said in a statement posted on her Twitter account.

Referring to her meeting with Babak, Siamak’s brother, on June 15, Haley affirmed, “Today we met Babak Namazi, whose brother and 81-year-old father who spent his career working on behalf of the world’s children at UNICEF have been imprisoned by Iran.”

Insisting that “no family should have to experience this,” Haley emphasized “if they [Iran] want to have any credibility in the world, they will let Baquer and Siamak come home.”

Siamak Namazi, former director of the strategic planning department at the Crescent oil company, was detained by Iranian security forces in October 2015 while visiting family in Iran.

Four months later, Baquer Namazi, who had apparently traveled to Iran to follow up his son’s case in the hope of negotiating his release, was also detained.

Baquer Namazi, a former UNICEF official, was a governor under Shah Mohammed Reza Pahlavi, who was overthrown in 1979, and immigrated to the United States in 1983. He reportedly has heart problems.

In October 2016, Siamak was tried and sentenced to 10 years in prison for espionage and collaborating with an unnamed foreign government.

Four months later, it was revealed that Baquer Namazi had also been taken into custody by Iranian security forces and charged with espionage.

Later, it was reported that he had also been tried and sentenced to 10 years’ prison.

In a written statement on behalf of the family, Babak Namazi called the sentences unjust. “My father has been handed practically a death sentence,” he wrote. “Siamak’s only crime has been to speak out against the negative effects of sanctions [imposed by the United States on Iran for violating its nuclear commitments].”

Babak Namazi also wrote in his statement that the trial had lasted only “a few hours.”

Recently, in May, while Washington was preparing itself for the first round of the Trump administration’s nuclear talks with Tehran, the Namazis’ attorney called on the White House to pressure Iran for the release of his clients.

On April 26, their attorney, Jared Genser, alongside Siamak’s brother, traveled to Vienna, where the nuclear talks were scheduled to take place. There, once again, Genser raised concerns over the Namazis’ poor health condition and called U.S. representatives to raise the case with Tehran and exert pressure for their immediate release.

Washington and Tehran later confirmed reports concerning talks about the case on the sidelines of their nuclear negotiations in Vienna.

Prior to Haley’s tweet, in a bipartisan resolution, U.S. Congress called on Trump’s administration to act in a specific way to secure the release of all Iranians with dual citizenship who are currently held in Iranian prisons.

Reportedly, most if not all of these detainees were arrested by agents connected with the Islamic Revolutionary Guard Corps (IRGC) since the Joint Comprehensive Plan of Action, Tehran’s nuclear deal with the world powers, was struck in 2015.

According to the draft resolution in Congress, IRGC agents detained Siamak Namazi, Baquer Namazi, Karen Vafadari, and a fourth person whose identity has not yet been publicly revealed.

Two other people, Afarin Niasari and Nizar Zakka, who are U.S. permanent residents, have also been taken hostage by IRGC agents, the draft maintains.

Zakka, a Lebanese green-card holder (a permanent resident of the United States) and advocate of Internet freedom, disappeared in Iran in September 2015 after attending a conference in Tehran.

The draft resolution also refers to citizens of other countries still held in Iran, including the United Kingdom, Canada, Germany, and France. The draft calls for these countries to join the United States to launch a united front for common efforts toward the release of all Iranians with dual citizenship incarcerated in Iranian prisons.